Several patents and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents and publications is incorporated by reference herein.
Ionomeric films are commonly supplied in roll form. These ionomer films, however, are usually intended to be converted into packaging, such as food or medical packaging, for example. In these applications, the packaging film may be required to do little more than shield the package contents from dirt, or prevent the packaged items from becoming separated. Therefore, the thickness of these ionomeric films may be very small, for example up to about 15 mil or about 400 micrometers.
When ionomeric sheets are used as interlayers in laminated structures, however, the required properties may be more stringent. For example, in safety laminates, impact resistance and penetration resistance are required. Load bearing ability may also be required, as when the laminates are used in staircases and viewing platforms. In photovoltaic devices, particularly in solar cell modules that are incorporated into windows, the properties required of the ionomeric encapsulant may be similar.
Therefore, the thickness of ionomeric sheets used as interlayers in safety laminates and as encapsulants in solar cell modules is generally substantial. Sheets having thicknesses of 30 to 120 mil (762 to 3048 micrometers) are commonly used in automotive and architectural applications. When greater penetration resistance is required, for example in architectural glazing for hurricane-prone areas or in bullet-resistant glass, thicknesses of up to 20 mm (2.0×105 micrometers) may be necessary.
Ionomeric materials for use as interlayers and encapsulants have previously been supplied as sheets that are pre-cut to standard sizes that approximate the desired size of the laminated safety glass or photovoltaic device. This form is inconvenient and wasteful, however. In particular, the ionomeric materials are typically extruded as continuous sheeting, which is then trimmed to sheets of a uniform size. The trimmings are discarded or re-processed. Also, it is more difficult to count, stack, package and ship large numbers of flat sheets than it is to manufacture rolls of sheeting and transport the rolls to end users. In addition, pre-cut ionomeric sheets are generally interleaved between glass lites by hand to form the individual pre-press assemblies that are adhered together through heat and pressure to form the safety glass laminate or photovoltaic device. Providing the ionomer as a roll of sheeting enables semi-continuous automated methods of producing these laminates.
Accordingly, there remains a need to develop new forms of ionomeric sheets, in particular, relatively thick ionomeric sheeting that can be taken up into a roll and supplied in continuous form.